The present invention relates to paint spray systems, most typically but not necessarily of the electrostatic type. More particularly, the invention relates to a new and improved system for effecting a color change cycle in an industrial paint spray system, in a manner permitting segregation and separate collection of the residual paint remaining in the system at the commencement of a color change cycle.
In the R. F. Wiggins U.S. Pat. No. 3,348,774, owned by the assignee of the present invention, an advantageous arrangement is shown for effecting a color change cycle in an industrial painting system. This arrangement includes an in-line valve manifold containing a series of paint color valves, as well as purge valve means for solvent and air. When it is desired to change over the system from one paint color to another, a cycle control is initiated to sequentially terminate the supply of original paint, flush out the system with solvent, and possibly also with air, and introduce paint of a new color into the system. To avoid having to discharge a substantial volume of paint and solvent into the spray booth area, discharge conduits are provided, communicated with the spray devices only substantially at the spray nozzle, immediately upstream of the discharge valves for the nozzles. When a color change cycle is initiated, the spray nozzle valves are closed and so-called "dump" valve means in the discharge lines are opened, enabling the original paint and the cleaning solvent to be discharged from the dump valve and into a suitable receptacle. The new paint flows through the system until it commences to flow into the discharge line, on the downstream side of each spray gun, after which the dump valve means can be closed and the spray nozzles re-opened.
In prior color change systems, there has been no convenient facility for easily segregating and separately collecting the unused paint of an original color, as it is purged from the system in preparation for a new color. While, of course, it has been theoretically possible to accomplish this, the practical economics of performing an effective segregation with existing equipment has not been favorable.
As a feature of the present invention, a novel, yet highly simplified arrangement is provided which enables successive colors to be readily isolated from each other, and effectively and separately collected, all as a part of a substantially automatic cycle requiring a relative minimum amount of time and operator attention. In part, this is achieved by providing a pair of spaced trap valves, with an "inventory line" of substantial length connected therebetween and desirably formed of transparent or translucent material. During the course of a color change cycle, it is readily possible to time with the cycle timer the purging of the existing paint through the inventory line, and the subsequent entry into the inventory line of the new color paint. When the new color has entered the inventory line, the timer then closes both trap valves. This provides for an uninterrupted column of paint upstream of the inventory line and complete segregation of the original paint downstream of the inventory line. Upon closing of the trap valves, the painting system may be reactivated to apply the new color at the spray station. Independently, additional purging solvents and fluids may be introduced downstream of the inventory line to effect thorough clean out of the discharge line in preparation for a subsequent color change cycle.
To advantage, the system of the invention permits all of the paint recirculation and supply functions to be confined substantially within a segregated paint mix room or area although such is not required by the invention. Moreover, the discharge section of this system may terminate remotely, within the paint mix room, so that all paint mixing and handling functions can be accomplished entirely remote from the spray area.
In cases where a relatively elaborate system is desired, the segregation and separate collection of paints, during a color change cycle, may be sequenced in such manner that the purged material is discharged back into a segregated auxiliary paint supply associated with the vessel from which the paint was supplied in the first instance. In a more economical system, suitable for many applications, purged paint is segregated into separate vessels and remixed at a subsequent convenient time.
In those instances where the purged materials are to be returned a substantial distance to a remotely located mixing room, the trap valves and inventory line are, according to the invention, located in reasonably close proximity to the spray booth area. This maintains at a minimum the volume of new paint required to properly charge the system in preparation for painting of a new color, and thus tends to minimize the increments of paint required to be purged when a color change cycle is effected.
The system of the invention is readily adaptable to effecting sequential color change cycles in a series of paint stations. Thus, the system is ideally suited for typical industrial paint spray installations, in which a plurality of paint spray stations are located at spaced positions along a conveyor route.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description, and to the accompanying drawings.